The present invention relates to periscopes such as used onboard submarines, more particularly to methods and apparatuses for sealing a periscope to prevent infiltration of water into the submarine hull.
A periscope is an optical device for enabling a user to observe objects that are otherwise outside the field of view of the user. The optics of a periscope may involve lenses, mirrors, and/or prisms. According to traditional operation of a periscope onboard a naval submarine, the vertical periscope protracts upward from the submarine hull to permit observation above the water surface while the submarine is submerged, and retracts downward into the submarine hull when the periscope is not in use, such as while the submarine is afloat.
A periscope must be sealed with respect to the submarine hull opening. The terms “hull packing system” and “hull fitting system” are used synonymously herein. A hull packing system must be implemented to completely separate the two fluid media (viz., the water surrounding the submarine, and the air contained in the submarine), particularly when the submarine is deeply submerged. The components of a hull packing system must be arranged and aligned so that the periscope is capable of being raised and lowered and trained, with minimal risk of leakage, while the submarine is submerged. The water must be maintained outside the submarine, the atmospheric air must be maintained inside the submarine, and flooding of the submarine must be prevented.
Periscope hull packing systems previously implemented by the United States Navy were designed for older classes of ships. The hull packing was cumbersome to maintain, was susceptible to seal-side loading and rolling, caused high training torque, resulted in high maintenance costs, required frequent greasing, and included many parts. Because there were so many parts, the removal and installation of the hull packing was more labor consuming than desired.
A number of failures were related to the Navy's old hull packing designs, especially with the incompatibility of the seals with respect to the cavities of newer submarines. In general, rolled seals (e.g., secondary seals and salvage seals) result in excessive training torque; Navy investigations attributed many seal failures to rolling of the seals. Because of problems such as these, many periscopes were removed from submarines and were reinstalled with repacked hull fittings.
Incorporated herein by reference are the following United States patents that are of interest with regard to sealing systems for periscopes: Kollmorgen U.S. Pat. No. 1,514,621 issued 11 Nov. 1924; Williams U.S. Pat. No. 2,173,192 issued 19 Sep. 1939; Gilbert, Sr. U.S. Pat. No. 2,568,392 issued 18 Sep. 1951; Janise U.S. Pat. No. 2,791,194 issued 7 May 1957; Peterson U.S. Pat. No. 2,936,187 issued 10 May 1960; Pratt U.S. Pat. No. 4,771,721 issued 20 Sep. 1988; Pratt U.S. Pat. No. 4,848,886 issued 18 Jul. 1989.